There are known key switches, comprising a housing, an actuation key, a switching member and a means for returning the key into its initial position. With switches of this kind manual input of information involves acting upon the key to move the movable part of the switch, thus acting upon the switching member to make or to break the external electric circuit. Depending on the actual application of the key switch, it may have for its switching member various contact and contact-free devices, e.g. sealed-contact reed relays, inductance or capacitance transducers, photoelectric or magnetically responsive switches, and so on. The means for returning the key into its initial position in most cases is in the form of a compression spring which is subjected in operation to two-sided resilient deformation and thus curbs down the service life of the key switch, whereas the mechanical characteristic of this switch (i.e. the curve of the distribution of the static load vs. the stroke of the key) defined by the compression of the spring and featuring the rising resistance to the displacement of the key would not promote the positive actuation of the key to its required extreme or endmost position, while affecting the vibration-proof rating of the key switch and not giving the operator a distinct "feel" of the key switch having operated, i.e. of the area where the switching member is actuated; in other words, the required reliability of the input of information is not provided for in full.
There is known a key switch (cf.USSR Inventor's Certificate No. 409,302; Int.Cl..sup.2 H01H 13/28, dated Dec. 30, 1973) comprising a housing, an actuation key rigidly connected with a permanent magnet or several permanent magnets accommodated in the housing, a magnetically responsive switching member mounted in the housing and adapted to be acted upon by the permanent magnet or magnets as the key is displaced, means for retaining the key in its initial position, including a plate of a soft-magnetic material mounted in the housing intermediate the key and the magnet or magnets, and means for returning the key into its initial position, including a compression spring.
As compared with the first-mentioned type of key switches, the abovedescribed key switch offers an improved vibration-proof rating and the reliability enhanced by the incorporation of the key-retaining means. However, the presence of the compression key-returning spring still affects the service life or durability of the key switch, complicates its structure and would not provide for having an ergonomically attractive mechanical characteristic promoting error-proof input of information.